1. Field of the Invention
The present invention relates to liquid crystalline compounds comprising a polymerizable functional group and 2-trifluoromethyl- or 2-difluoromethyl-1,4-phenylene, as well as to compositions comprising the compounds, and their polymers and uses thereof.
2. Related Art
Polymerization of polymerizable liquid crystal compounds aligned in the nematic state yields polymers having fixed alignment states and exhibiting optical anisotropy. Polymers with optical anisotropy are employed as optical compensation films for liquid crystal display elements. One commonly used polymerizable liquid crystal compound is 1,4-bis(4-(substituted)-benzoyloxy)benzene (see Non-patent document 1, Patent document 1).
On the other hand, the optical compensation film must have optimum alignment, depending on the construction and purpose of use of the liquid crystal display element, in order to exhibit its maximum optical compensation function. Specifically, it is necessary to exhibit planar, homeotropic, hybrid, tilted and twisted alignments at appropriate times. The state of alignment is determined by the chemical structure of the material. Polymerizable compounds have therefore been desired which easily exhibit desired alignments (see Patent document 2).
Monofunctional polymerizable liquid crystal compounds containing 2-trifluoromethyl- or 2-difluoromethyl-1,4-phenylene, compounds with sulfoxyl groups, compounds with urethane bonds, compounds with —C≡C— among the bonding groups, compounds with silacyclohexane rings and compounds with —N═N— among the bonding groups are disclosed in the prior art documents listed below (see Patent documents 1,3–7).    Patent document 1: U.S. Pat. No. 6,491,990    Patent document 2: JP-A 8-3111/1996    Patent document 3: JP-A 332484/2002    Patent document 4: JP-A 212561/2002    Patent document 5: JP-A 3845/2002    Patent document 6: EP466183    Patent document 7: EP1209515    Non-patent document 1: Macromoleculare Chemie 1989, 190, 2255–2268
Nevertheless, no polymerizable liquid crystal compounds have been known which easily exhibit desired molecular alignments. It is an object of the present invention to solve this problem of the prior art.